Download Boating Tip #54: Telltales (PDF format, 18KB)

Telltales are strips of ripstop nylon, tape, pieces of yarn, or other lightweight material that are attached to sails to help determine whether a sail is properly trimmed. They help a sailor see the air moving across a sail. Correctly trimmed sails produce an improvement in performance and boat speed.

Telltales are sometimes also attached to shrouds to indicate apparent wind direction.

Telltales are usually fastened to a sail with waterproof tape or an adhesive patch. On a headsail, sets of telltales are placed ¼, ½ and ¾ of the way down the sail about one foot aft of the luff. Typically a green telltale is attached on the starboard side of the sail, and a red tail on the port side. On a mainsail, three or four telltales are attached and evenly spaced down the leach so that they stream out behind the sail.

By looking at the telltales, your can determine if you are sailing too close to the wind, and whether a sheet needs to be pulled in or let out. When the sail is trimmed properly, the telltales all fly aft and flutter parallel to the water. If the telltales are all flying straight aft, the sheets can be eased slightly.

If the main is not properly trimmed, the telltales will stall and droop down or blow forward.

If the headsail is not trimmed correctly, the telltales will tell you what corrective action must be taken. If the telltales on the windward side of the sail are lifting, you are either pointed too high into the wind, or the sail is let out too far. If the telltales on the lee side are lifting, you are sailing too low or the sail is pulled in too tight. Either adjust the sails or correct your course direction.

Telltales can also help you determine is the fairleads are in the correct position for the existing wind conditions. While sailing close hauled, you should be able to adjust the sail so that all three sets of telltales on the headsail are flying parallel to the water. If the fairleads are positioned too far forward, the highest leeward and lowest windward telltales will flutter around. If the fairleads are positioned too far aft, the opposite will occur. The highest windward and lowest leeward telltales will flutter.